Caption: Rhabdomyosarcoma cancer cells, coloured scanning electron micrograph (SEM). This aggressive cancer arises from primitive skeletal muscle cells (rhabdomyoblasts). It is a childhood cancer that is more common in boys than girls. Tumours cause painless masses under the skin, most often around the head and neck and genitourinary tract. Treatment is with chemotherapy, often combined with surgical removal of the tumour and radiotherapy. Magnification: x1,330 when printed at 10 centimetres wide.